In the prior art, it is known that optical information may be recorded or written in a thermoplastic layer by controlling the three parameters of surface charge density, light density and temperature of the thermoplastic layer -- see the A. E. Jvirblis, et al., U.S. Pat. No. 3,795,514. More recently, work has indicated that holographic recording on thermoplastic layers or films may be the basis of future high-density holographic storage of analog and digital data. See the publications "Holographic Recording on Thermoplastic Films," T. C. Lee, Applied Optics, Volume 13, No. 4, April, 1974, Pages 888-895, and "An Experimental Read-Write Holographic Memory," W. C. Stewart, et al., RCA Review, Volume 34, March, 1973, Pages 3-44.
In the past, it was known to apply thermal energy to selective recording areas of a thermoplastic layer using a matrix array of resistive heating elements. This configuration requires at least two electrical connections per selected recording area. Accordingly, in an optical data storage system of reasonable size, the number of electrical connections would be near prohibitive with a significant portion of the area of the thermoplastic layer being required for such electrical connections. In the L. D'Auria U.S. Pat. No. 3,878,515 there is disclosed a thermoplastic storage system wherein each recording area of a thermoplastic layer along a given row is coupled to a pair of electrical busbars, each recording area including an electrical heating element and a photoconducting switching element. When the photoconducting switching element is exposed to a beam of light, the two associated busbars are intercoupled causing current to flow through the electrical heating element and, accordingly, to apply thermal energy to the associated recording area. However, this most recent system still requires that an inordinate portion or amount of the area of the thermoplastic layer be utilized by the busbars and related electrical apparatus including the thermal conducting switching element.
In the R. W. Honebrink, et al., U.S. Pat. No. 4,053,872 there is disclosed an apparatus for and a method of recording or writing optical data into a thermoplastic layer. The apparatus includes a layer of photoconductive material that is photoconductively responsive to a data-containing light beam having a wavelength below the IR range and a layer of thermoplastic material that is thermoplastically responsive to a light beam having a wavelength within the IR range. In practicing the method of that invention, the electrically charged apparatus is exposed to a data-bearing light beam having a wavelength below the IR range for selectively exposing, i.e., electrically charging, the photoconductive layer. Next, the apparatus is exposed to a light beam having a wavelength within the IR range for heating the thermoplastic film and thermally permitting the selective electric charge in the photoconductive layer to distort the surface of the thermoplastic layer and, accordingly, write into the thermoplastic layer the optical data that was contained within the data-bearing light beam.
In the publication "The EPIM TOPR In Optical Data Processing," G. D. Currie, et al., Proceedings of the Society of Photo-Optical Instrumentation Engineers, Volume 83, Aug. 24-25, 1976, Pages 8-12, there is disclosed an apparatus for and a method of optically recording or writing data into a thermoplastic layer that is formed as an integral part of the face of a CRT. In this system, the vacuum side of the CRT face is coated with a transparent conductor that serves as the anode for the electron beam and that provides resistive heating to the thermoplastic layer. Next, upon the transparent conductor there is coated a thermoplastic layer of a few microns (.mu.m) in thickness. In the method of this system, the entire active area of the thermoplastic layer is scanned by an intensity-modulated, data-bearing electron beam after which the entire active area is resistively heated by the transparent conductor to the deformable state. Thus, both the charging and the heating steps are performed over the entire active area of the thermoplastic layer. This simultaneous heating of the entire active area of the thermoplastic layer requires the application of an inordinate amount of instantaneous heating energy followed by a relatively long period of dissipation (cooling) of the heating energy prior to a read operation and a subsequent erase-write-read operation. The present invention is directed toward an improvement to this system.